Riboflavin derivatives and process of preparing the same



Patented Apr. 16, 1946 RIBOFLAVIN DERIVATIVES AND PROCESS OF PREPARINGTHE SAME Gerhard Julius Haas, New York, N. Y., assignor to Hofi'mann-LaRoche, Inc., Roche Park, Nutley, N. J., a corporation of New Jersey NoDrawing.

Application April 27, 1945,

Serial No. 590,745

19 Claims.

This invention relates to new soluble derivatives of riboflavin (vitaminB2) having considerably increased solubility in solvents, such as water,aqueous alcohol, glycerine and th like, and to a process of making them.

It is well known that the therapeutic use of riboflavin in solutions isseverely restricted owin to its low solubility in all physiologicallyacceptable solvents, such as water, aqueous alcohol, glycerine and thelike. Attempts have been made to increase the solubility of theriboflavin in these solvents, either by preparing derivatives ofriboflavin having groups which increase the solubil-.

and the salts of these derivatives, wherein n is a number from to 3inclusive, R1 is a divalent aliphatic radical, and R2 and R3 arehydrogen, alkyl, hydroxyalkyl or aminoalkyl, have exceptionally highsolubilities in the aforementioned customary solvents, particularly inwater.

My new derivatives can be Prepared by esterifying riboflavin with ahalogenide of the general formula X.R1.COX where R1 has the meanin givenabove and X stands for halogen such as above. In this way, halogenatedderivatives of riboflavin are prepared which may or may not be actuallyisolated. The number of substituents, designated by the numeral n above,depends on the quantity of the above esteriiying agents used. In mypreferred modification I use 4 g. equivalents of these'esterifyingagents for 1 g. equivalent of riboflavin.

These compounds are then reacted with allphatic amines. In this way, thehalogen is displaced and mixed amines of esterlfled riboflavin areobtained. These amines are extremely soluble. particularly in the formof their salts. These salts may be isolated or directly used insolution. Thus, for instance, the citrate of Bz-acetyl-diethylamine isobtained by reacting riboflavin with 4 g. mols of chloracetyl chloride,reacting the condensation product with diethylamine and chlorine orbromine, or with halogenated acid anhydrides of the general formulaX.R1C0

, o xnlco wherein X and R1 have the meanings indicated treating the basewith citric acid. I have found that up to mg./cc. of riboflavin can bepresent in aqueous solutions of this citrate, and to my knowledge thisvalue represents one of the highest solubilities of riboflavin in waterthus far achieved. Moreover, such a highly concentrated aqueous solutionmay be prepared at the low pH values of 3.5 and 4 which are particularlyuseful for liquid vitamin-complex preparations.

The following examples illustrate my invention:

EXAMPLE 1 Citrate of diethylaminoacetyl-riboflavin 50 g. of dryriboflavin were suspended in cc. dry dioxane, and to this suspension41.5 cc. (62 g.) (4.13 g. mols) chloracetylchloride in 100cc. drydioxane were added and the mixture refluxed for 1% hours shakingoccasionally during this interval. Then all the dioxane was distilledoff in vacuo and the residue washed once with ether. At this stage asample shaken with water should not give an acid reaction, thus showingthat all the HCl has been removed. The residue was then treated withexcess diethylamine. It went into solution and at the same timediethylamine hydrochloride was precipitated. The diethylaminehydrochloride was filtered oil? and the filtrate evaporated to drynessin vacuo. The residue was dissolved in acetone. This solution was thenadded with stirring to a solution 01' excess citric acid in acetone. Theprecipitate settled to the bottom as a dark semisolid residue. It wasthen redissolved in a minimum of methanol, decolorized with charcoal,and reprecipitated with acetone. The substance precipitated as aflocculent precipitate, it was filtered, immediately transferred to thedesiccator and finally dried at 1 mm. and 60- for 30 minutes. Theresulting compound was a reddish-brown powder decomposing above 118 C.uncorr., giving reddish- Citrate of diethylaminoacetyl-riboflavin g. ofchloracetyl-Bz were dissolved in 15 cc. of diethylamine, and theprecipitated diethylamine hydrochloride filtered oil. The excessdiethylamine was then evaporated oil, and the residue dissolved inacetone and precipitated with ether. The precipitated oil wasredissolved in acetone and added to a solution of 5 g. of citric acid inacetone. The citrate precipitated out as a sticky mass. It was dried inthe desiccator, dissolved in methanol and reprecipitated with acetone.It was similar in properties to the compound obtained in Example 1.

EXAMPLE 3 Hydrochloride of dithylaminoaeetyl-Hboflavin g. of B2 wereesterifled with 8.45 cc. (12.6 g., 4.2 mol equivalents) oi chloracetylchloride in dioxane, as described in Example 1.

After distilling oil the dioxane, the residue was dissolved indiethyiamine, the precipitated diethylamine hydrochloride filtered oiland the filtrate evaporated to dryness in high vacuo. The residue wasthen dissolved in dilute HCl. It may now be adjusted to the pH value,and to the concentration which it is desired to use. Samples containing5.5 mg./cc. of riboflavin, as determined fluorometrically, did notprecipitate on storage for a period of 21 days at 4 0., 25 C., 40 C. or45 C.

EXAMPLE 4 Citrate of (alpha diethylaminopropimwl) riboflavin 1 g. of thereaction product of riboflavin with 4 g. mols a-brompropionyl bromideCHaCHBrCOBr was treated with a mixture of methanol and diethylamine.When the solution was homogeneous, it was evaporated to dryness and theresidue dissolved in acetone; this acetone solution was then added to asolution of citric acid in acetone. The citrate precipitated out, andwas also very soluble inwater just as the product described in Example1.

EXAMPLE 5 Hydrochloride of diethylaminoacetyl-riboflavin 10 g. ofriboflavin were esterifled with 8.5 cc. of chloracetyl chloride indioxane, as described above. The chloroacetyl compound was thendissolved in diethylamine by shaking. the diethylamine hydrochlorideformed was filtered off, and the excess diethylamine was distilled offin vacuo. The residue was dissolved in a saturated solution of hydrogenchloride gas in methanol. The hydrochloride ofdiethylaminoacetyl-rlboflavin was then precipitated with acetone as ablackishbrown oily precipitate. It was redissolved in methanol andreprecipitated with acetone as a flocculent reddish-brown hygroscopicprecipitate, which decomposes when heated above 155 C. uncorr. in vacuo.It was extremely soluble in water (1 g. in 1 cc.). (pH about 1.8)

The solutions were acid Exem t: 6

Aminoacetyl-riboflavin 3 g. or chloracetyl riboflavin were refluxed in30 cc. of dioxane with 2 cc. of concentrated ammonia solution; after /2hour refluxing the mixture was evaporated down in volume and so most oithe excess ammonia driven on. Then ether was added and theaminoacetyl-riboflavin precipitated. The supernatant liquid was removedby decantation, then methanol was added to the precipitate. The mainportion went'into solution.

After filtering ofl the insoluble portion, the aminoacetyl-riboflavinwas precipitated with ether. A flocculent precipitate very soluble inwater resulted.

What I claim is:

1. Riboflavin derivatives selected from th group consisting of thosecorresponding to the following general formula, and of their salts /R2CHzOOCRxN HOOCRiN\ R! I HOHh-n N N on T E NH 1 group consisting of thoseof lower halogenalkyl esters of riboflavin with aliphatic amines, and oftheir salts.

4. Condensation products selected from the group consisting of those oflower chloroalkyl esters or riboflavin with aliphatic amines, and oftheir salts.

5. Condensation products selected from the group consisting of those oflower bromoalkyl esters of riboflavin with aliphatic amines, and oftheir salts.

6. Condensation products selected from the group consisting of those oflower halogenallwl esters of riboflavin with diethylamine, and of theirsalts.

7. Condensation products selected from the group consisting of those oflower halogenalkyl esters of riboflavin with a compound or the generalformula consisting of hydrogen and ethyl and of their salts.

8. Riboflavin derivatives selected from the group consisting of thosecorresponding to the riboflavin which comprises esterifying riboflavinfollowing general formula, and of their salts with a bromide of thegeneral formula Br.R1.COBr CH OQQmN 5 wherein R1 is a divalent loweraliphatic radical, and reacting the resulting ester with an aliphaticamine.

13. Process for making soluble derivatives of 0300011: riboflavin whichcomprises esterifying riboflavin 3 with an esterifying agent selectedfrom the group :132 consisting of halogenated lower fatty acid halo- N Ngenides and halogenated lower fatty acid anhycn=- V .drides, andreacting the resulting ester with di- I l ethylamine.

CHa N C 1 14. Process for making citrate ofdiethylaminoacetyl-ribofiavin which comprises esterifying 1 mol ofriboflavin with slightly more than 4 wherein R1 is a divalent loweraliphatic radical mols of chloracetyl chloride in dioxane, removand R2and R3 are selected from the group coning the dioxane, treating theresidue with an sisting of hydrogen and ethyl. excess of diethylamine,filtering all the precipi- '9. Process for making soluble derivatives oftated diethylamine hydrochloride, evaporating riboflavin which comprisesesterifying riboflavin the filtrate to dryness, and reacting the residuewith an esterifying agent selected from the group in acetone solutionwith an excess of citric acid. consisting of halogenated lower fattyacid halo- 15. Process for making hydrochloride 0f hgenides andhalogenated lower fatty acid anhyylaminoacetyl-riboflavin whichcomprises esteridrides, and reacting the resulting ester with a. fying 1mol of riboflavin with slightly more than compound corresponding to thegeneral formula 4 mols of chloracetyl chloride in dioxane, removing thedioxane, treating the residue with an excess of diethylamine, filteringoff the precipitated EN 39 diethylamine hydrochloride, evaporating thefiltrate to dryness, dissolving the residue in a sat- Q urated solutionof hydrogen chloride in methanol, wherein R2 and R3 are'selected fromthe group n precipitating the hy r e i y consisting of hydrogen andethyl. aminoacetyl-ribofiavin with acetone.

10. Process for making soluble derivatives of 85 PIOCQSS for makingaminoacetyl-riboflavin riboflavin which comprise esterifying riboflavinWhich Comprises ,esterifyihg 1 1 1 1 f riboflavin with a halogenide ofthe general formula, with slightly more than 4 mols of chloracetylchloride in dioxane, distilling off the dioxane and X.Ri.COXrecrystallizing the resulting residue from meth- 40 anol, whereby a fineyellow crystalline powder wherein R1 is a divalent lower aliphaticradical was isolated, and refluxing said powder i i and X St nds fhalogen, and reacting e oxane with concentrated ammonia solution,drivult ester With an aliphatic amineing oil the excess ammonia from thesolution 11. Process for making soluble derivatives of and precipitatingthe aminoacetyl-riboflavin from riboflavin which comprises esterifyingriboflavin the solution by addition of ether.

with a chloride of the general formula Cl.Ri.COCl, 17,. c t t ofdiethylaminoacetyl-ribofiavin, wherein R1 is a divalent lower aliphaticradical, 13, Hydrochloride of diethylaminoacetyl-riboand reacting theresulting ester with an aliphatic flavin. amine. 19.Aminoacetyl-riboflavin.

12. Process for making soluble derivatives of GERHARD JULIUS HAAS.

